Jet plasma process and apparatus for deposition of coatings and the coatings thereof

ABSTRACT

The present invention provides a method for the formation of an organic coating on a substrate. The method includes: providing a substrate in a vacuum; providing at least one vaporized organic material comprising at least one component from at least one source, wherein the vaporized organic material is capable of condensing in a vacuum of less than about 130 Pa; providing a plasma from at least one source other than the source of the vaporized organic material; directing the vaporized organic material and the plasma toward the substrate; and causing the vaporized organic material to condense and polymerize on the substrate in the presence of the plasma to form an organic coating.

FIELD OF THE INVENTION

[0001] The present invention relates to coatings, particularly organiccoatings containing carbon and/or silicon coatings, and to a method andapparatus for the plasma deposition of such coatings.

BACKGROUND OF THE INVENTION

[0002] Plasma processes offer the opportunity to make coatings that canbe quite hard, chemically inert, corrosion resistant, and impervious towater vapor and oxygen. These are often used as mechanical and chemicalprotective coatings on a wide variety of substrates. For example,carbon-rich coatings (e.g., diamond-like carbon and jet plasma carboncoatings) have been applied to rigid disks and flexible magnetic media.They have also been applied to acoustic diaphragms, polymeric substratesused in optical and ophthalmic lenses, as well as electrostaticphotographic drums. Silicon-containing polymer coatings have beenapplied to polymeric and metal substrates for abrasion resistance. Also,silicone coatings have been applied to polymeric and nonpolymericsubstrates to reduce water permeability and to provide mechanicalprotection.

[0003] Carbon-rich coatings, as used herein, contain at least 50 atompercent carbon, and typically about 70-95 atom percent carbon, 0.1-20atom percent nitrogen, 0.1-15 atom percent oxygen, and 0.1-40 atompercent hydrogen. Such carbon-rich coatings can be classified as“amorphous” carbon coatings, “hydrogenated amorphous” carbon coatings,“graphitic” coatings, “i-carbon” coatings, “diamond-like” coatings,etc., depending on their physical and chemical properties. Although themolecular structures of each of these coating types are not alwaysreadily distinguished, they typically contain two types of carbon-carbonbonds, i.e., trigonal graphite bonds (sp²) and tetrahedral diamond bonds(sp³), although this is not meant to be limiting. They can also containcarbon-hydrogen bonds and carbon-oxygen bonds, etc. Depending on theamount of noncarbon atoms and the ratio of sp³/sp² bonds, differentstructural and physical characteristics can be obtained.

[0004] Diamond-like carbon-rich coatings have diamond-like properties ofextreme hardness, extremely low electrical conductivity, lowcoefficients of friction, and optical transparency over a wide range ofwavelengths. They can be hydrogenated or nonhydrogenated. Diamond-likecarbon coatings typically contain noncrystalline material having bothtrigonal graphite bonds (sp²) and tetrahedral diamond bonds (sp³);although it is believed the sp³ bonding dominates. Generally,diamond-like coatings are harder than graphitic carbon coatings, whichare harder than carbon coatings having a large hydrogen content, i.e.,coatings containing hydrocarbon molecules or portions thereof.

[0005] Silicon-containing coatings are usually polymeric coatings thatcontain in random composition silicon, carbon, hydrogen, oxygen, andnitrogen (SiO_(w)N_(x)C_(y)H_(z)). These coatings are usually producedby plasma enhanced chemical vapor deposition (PECVD) and are useful asbarrier and protective coatings. See, for example, U.S. Pat. Nos.5,298,587 (Hu et al.), 5,320,875 (Hu et al.), 4,830,873 (Benz et al.),and 4,557,946 (Sacher et al.).

[0006] Silicone coatings are high molecular weight polymerized siloxanecoatings containing in their structural unit R₂SiO in which R is usuallyCH₃ but may be H, C₂H5, C₆H₅, or more complex substituents. Thesesilicones (often referred to as polyorganosiloxanes) consist of chainsof alternating silicon and oxygen atoms (O—Si—O—Si—O) with the freevalences of the silicon atoms joined usually to R groups, but also tosome extent to oxygen atoms that are joined to (crosslinked) siliconatoms in a second chain, thereby forming an extended network. Thesecoatings are valued for their toughness, their lubricity, controlled gasdiffusion, and their ability to lower surface tension desirable forrelease coatings and water repellent surfaces. For example, U.S. Pat.No. 5,096,738 (Wyman) teaches the formation of barrier coatings via thehydrolysis of trialkoxy methyl silane resulting in highly crosslinkedpolymer structures.

[0007] Methods for preparing coatings by plasma deposition, i.e.,plasma-enhanced chemical vapor deposition, are known; however, some ofthese methods have deficiencies. For example, with certain methods theuse of high gas flow, pressure, and power can cause formation of carbonpowder, instead of the desirable smooth, hard carbon film. U.S. Pat.Nos. 5,232,791 (Kohler et al.), 5,286,534 (Kohler et al.), and 5,464,667(Kohler et al.) disclose a process for the plasma deposition of acarbon-rich coating that overcomes some of these deficiencies. Theseprocesses use a carbon-rich plasma, which is generated from a gas, suchas methane, ethylene, methyliodide, methylcyanide, or tetramethylsilane,in an elongated hollow cathode, for example. The plasma is acceleratedtoward a substrate exposed to a radio frequency bias voltage. Althoughthis process represents a significant advancement in the art, otherplasma deposition processes are needed for deposition of a wide varietyof carbon- and/or silicon-containing coatings using lower energyrequirements.

[0008] Methods of preparing multilayer coatings are described in U.S.Pat. Nos. 5,116,665 (Gauthier et al.) and 4,933,300 (Koinuma et al.),and UK Patent Application Publication No. GB 2 225 344 A (EniricercheSpA). These methods are based on glow discharge processes, which utilizeone reactor and successive changes in process parameters for theconstruction of multilayer coatings. These methods, however, havepractical and technical limitations. A batch type process is required ifgradual and/or abrupt changes of layer properties are desired. Thosechanges are obtained by deposition on stationary substrates andsuccessive changes in process conditions. Continuous deposition can beobtained in a reactor that accommodates a roll-to-roll web transportsystem. Multipass operation is required to construct multilayercoatings. Under those circumstances a gradual change of layer propertiesand/or the formation of interfacial layers are difficult to obtain.

[0009] Thus, plasma deposition processes are needed for deposition of awide variety of carbon- and/or silicon-containing coatings usingrelatively low energy requirements. Also, plasma deposition processesare needed that can accommodate a gradual change of layer propertiesand/or the formation of interfacial layers.

SUMMARY OF THE INVENTION

[0010] The present invention provides a method for the formation of anorganic coating on a substrate comprising: providing a substrate in avacuum; providing at least one vaporized organic material comprising atleast one component from at least one source, wherein the vaporizedorganic material is capable of condensing in a vacuum of less than about130 Pa; providing a plasma from at least one source other than thesource of the vaporized organic material; directing the vaporizedorganic material and the plasma toward the substrate; and causing thevaporized organic material to condense and polymerize on the substratein the presence of the plasma to form an organic coating.

[0011] The step of providing a plasma preferably includes generating aplasma in a vacuum chamber by: injecting a plasma gas into a hollowcathode system; providing a sufficient voltage to create and maintain aplasma within the hollow cathode system; and maintaining a vacuum in thevacuum chamber sufficient for maintaining the plasma. In a preferredembodiment, the hollow cathode system includes: a cylinder having anoutlet end; a magnet surrounding the outlet end of the cylinder; and atube having a leading edge, wherein the tube is positioned inside thecylinder and recessed such that the leading edge of the tube is in theplane of the center line of the magnet.

[0012] Also provided is an organic coating on a substrate preparable by:providing a substrate in a vacuum; providing at least one vaporizedorganic material comprising at least one component from at least onesource, wherein the vaporized organic material is capable of condensingin a vacuum of less than about 130 Pa; providing a plasma from a sourceother than the at least one source of the vaporized organic material;directing the vaporized organic mate rial and the plasma toward thesubstrate; causing the plasma to interact with the vaporized organicmaterial and form a reactive organic species; and contacting thesubstrate with the reactive organic species to form an organic coating.The coating can include one layer of a single organic material ormultiple organic materials. Alternatively, it can include multiplelayers of different organic materials.

[0013] The present invention also provides a non-diamond-like organiccoating on a substrate comprising an organic material comprising atleast one major component, wherein the coating has a density that is atleast about 50% greater than the density of the major component of theorganic material prior to coating. For one component layer, thenon-diamond-like organic coating preferably has substantially the samecomposition and structure as that of the starting material.

[0014] The present invention also provides a jet plasma apparatus forforming a coating on a substrate comprising: a cathode system forgenerating a plasma; an anode system positioned relative to the cathodesystem such that the plasma is directed from the cathode system past theanode system and toward the substrate to be coated; and an oil deliverysystem for providing vaporized organic material positioned relative tothe cathode system such that the vaporized organic material and theplasma interact prior to, or upon contact with, the substrate.

[0015] The present invention further provides a hollow cathode systemcomprising: a cylinder having an outlet end; a magnet surrounding theoutlet end of the cylinder; a tube having a leading edge, wherein theceramic tube is positioned inside the cylinder and recessed such thatthe leading edge of the ceramic tube is in the plane of the center lineof the magnet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a schematic diagram of a jet plasma vapor depositionapparatus of the present invention.

[0017]FIG. 2 is an expanded perspective view of one preferred oildelivery system of the present invention.

[0018]FIG. 3 is an expanded perspective view of another preferred oildelivery system of the present invention.

[0019]FIG. 4 is a schematic diagram of an alternative jet plasma vapordeposition apparatus of the present invention.

[0020]FIG. 5 is a cross-sectional side view of a preferred hollowcathode point source of the present invention.

[0021]FIG. 6 is a plot of the effect of bias on moisture vaportransmission.

[0022]FIG. 7 is an Auger Spectroscopy depth profile of a coating of thepresent invention on a silicon wafer.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention provides methods and systems for formingorganic coatings, particularly carbon-containing coatings (e.g.,carbon-rich coatings as defined above), silicon-containing coatings(e.g., silicone coatings as defined above), or combinations thereof, andthe coatings themselves. The methods of forming the coatings occur bymeans of plasma interaction with a vaporized organic material, which isnormally a liquid at ambient temperature and pressure. The systems ofthe present invention can be used to deposit low cost coatings, whichcan have a wide range of specific densities. These coatings can beuniform multi-component coatings (e.g., one layer coatings produced frommultiple starting materials), uniform one-component coatings, and/ormultilayer coatings (e.g., alternating layers of carbon-rich materialand silicone materials).

[0024] Generally, the coating processes use a plasma (i.e., expandedgaseous reactive ionized atoms or molecules and neutral molecularfragments) and at least one vaporized organic material containing atleast one component, wherein the vaporized organic material is capableof condensing in a vacuum of less than about 1 Torr (130 Pa). Thesevapors are directed toward a substrate in a vacuum (either in outerspace or in a conventional vacuum chamber). This substrate is in closeproximity to a radio frequency bias electrode and is preferablynegatively charged as a result of being exposed to a radio frequencybias voltage. Significantly, these coatings are prepared without theneed for solvents.

[0025] For example, using a carbon-rich plasma in one stream from afirst source and a vaporized high molecular weight organic liquid suchas dimethylsiloxane oil in another stream from a second source, aone-pass deposition procedure results in a multilayer construction ofthe coating (i.e., a layer of a carbon-rich material, a layer ofdimethylsiloxane that is at least partially polymerized, and anintermediate or interfacial layer of a carbon/dimethylsiloxanecomposite). Variations in system arrangements result in the controlledformation of uniform multi-component coatings or layered coatings withgradual or abrupt changes in properties and composition as desired.Uniform coatings of one material can also be formed from a carrier gasplasma, such as argon, and a vaporized high molecular weight organicliquid, such as dimethylsiloxane oil.

[0026] The coatings formed using the jet plasma process described hereincan have a wide variety of properties. They can be tough, scratchresistant, chemically resistant, and suitable for use as protectivecoatings. They can be impermeable to liquids and gases, and suitable foruse as barrier coatings. They can have a controlled void/pore structureselective for molecular diffusion, and suitable for use as separationmembranes. They can be transparent and antireflective, and suitable foruse as an optical coating. They can have tailored surface energies andvariable conductivity and resistivity. Hence, the coatings can have awide variety of uses.

[0027] Preferred carbon-rich coatings and preferred silicone coatingsare impervious to water vapor and oxygen, and are generally resistant tomechanical and chemical degradation. They are also sufficiently elasticsuch that they can be used on typical flexible substrates used in, forexample, magnetic media and packaging films.

[0028] Such preferred coatings are highly polymerized and/or crosslinkedmaterials, i.e., materials having a crosslink density generally greaterthan that obtained if conventional methods of deposition, such asconventional PECVD methods, are used. Specifically, for example, thepresent invention provides a substrate on which is coated a siliconecoating, preferably a polymerized diorganosiloxane, having a highconcentration of crosslinked siloxane groups (i.e., high Si—O—Sicrosslinkage) and a reduced concentration of organic groups (e.g.,methyl groups) relative to the starting material.

[0029] Preferably, the coatings of the present invention arenon-diamond-like coatings yet generally very dense. The density of acoating is preferably at least about 10% (and more preferably, at leastabout 50%) greater than the major component of the organic materialprior to vaporization (preferably, greater than any of the startingmaterials). Typically, the organic starting materials are in the form ofoils, and the resultant coating can have a density that is preferably atleast about 10% (and more preferably, at least about 50%) greater thanthat of the oil used in the greatest amount. With methods of depositionthat do not expose the substrate to a radio frequency bias voltage,there is only a minor increase (e.g., less than about 10%) in thedensity of the coatings relative to the starting materials. Herein,density is measured by the floating method as described below. Preferredsilicone coatings of the present invention have a density of at leastabout 1.0.

[0030] Typically, as the radio frequency bias to which the substrate isexposed in the method described herein increases, the density andhardness of the coatings increase. As the density and hardness increase,the barrier properties for water vapor and/or oxygen (and other gases)increase. It is even possible to get several orders of magnitudeincrease in barrier properties and hardness using the methods of thepresent invention.

[0031] The present invention also provides a substrate on which iscoated polymerized mineral oil (i.e., an aliphatic hydrocarbon), such asNujol. This provides a decrease in water vapor transmission, which isbelieved to be associated with an increase in density. Thus, one organicmaterial that can be used as a starting material in the methods of thepresent invention is mineral oil. Other such organic materials includeother aromatic and aliphatic hydrocarbons as well as silicon- andoxygen-containing hydrocarbons such as silicone oil andperfluoropolyethers, which can be used alone or in combination. Suitableorganic materials are those that have strong bonds in the backbone thatdo not break down easily in a vacuum. They can be aromatic, aliphatic,or combinations thereof (e.g., compounds containing aralkyl or alkarylgroups). When more than one organic material is used, they can be mixedprior to vaporization and provided from one source or they can beprovided separately from separate sources.

[0032] Using the methods described herein, certain physical and chemicalproperties of the starting materials are generally maintained. That is,properties of the starting materials, such as coefficient of friction,surface energy, and transparency do not change significantly uponpreparing coatings using the methods described herein, as opposed toconventional plasma processes. Thus, the methods of the presentinvention are very different from conventional plasma processes becausethe molecules are not significantly broken down to low molecular weight,reactive, species with the methods of the present invention. Forexample, it is believed that the —Si—O—Si—O— chain of a silicon oilremains substantially in tact in the jet plasma process of the presentinvention.

[0033] The methods of the present invention include providing a plasma(e.g., an argon plasma or a carbon-rich plasma as described in U.S. Pat.No. 5,464,667 (Kohler et al.)) and at least one vaporized organicmaterial comprising at least one component from separate sources andallowing them to interact during formation of a coating. The plasma isone that is capable of activating the vaporized organic material. It canbe generated using well-known means or the point source describedherein. That is, the plasma can cause the vaporized organic material tobecome reactive, for example, as a result of radical formation,ionization, etc., although such reactive species are still capable ofcondensing in a vacuum to form a polymerized coating. Alternatively, theplasma can interact with the vaporized organic material as the vaporizedorganic material condenses on the surface in a manner such that theentire thickness of the coating is polymerized. Therefore, the plasmaand vaporized organic material can interact either on the surface of thesubstrate or prior to contacting the surface of the substrate. Eitherway, the interaction of the vaporized organic material and the plasmaprovides a reactive form of the organic material (e.g., loss of methylgroup from silicone) to enable densification of the material uponformation of the coating, as a result of polymerization and/orcrosslinking, for example. Thus, the method of the present inventionprovides the means of high rate deposition, approaching the condensationrate of the vaporized organic material; it also provides the means ofpreparing coatings where the physical and chemical composition andstructure of the precursor is maintained to a high degree.

[0034] The methods of the present invention preferably include the useof a radio frequency bias voltage sufficient to provide a coating havinga density that is at least about 10% greater (and preferably at leastabout 50% greater) than the density of the major component of theorganic material prior to vaporization. Preferably, the bias voltage isno more positive than about minus 50 volts, which also creates a plasmaat the substrate. More preferably, the bias voltage is no more positivethan about minus 100 volts, and most preferably, no more positive thanabout minus 200 volts. Typically, the bias voltage can be as negative asabout minus 2500 volts. The specific bias voltage typically depends onthe material of which the substrate is made. This high bias power can beobtained in conjunction with the use of the hollow cathode describedherein. As mentioned above, the higher the bias power the higher thedensity of the coating. With no bias, the density of a coating made bythe method of the present invention is very similar to that ofconventional coatings (e.g., a silicone polymer coating with nocrosslinkage) made by conventional processes (e.g., conventional PECVDmethods).

[0035] In general, high density coatings (e.g., diamond-like carbon, jetplasma carbon) are prepared by plasma enhanced chemical vapor deposition(PECVD), which utilize negatively biased substrates in contact withradio frequency powered cathodes. Typically, the system provides ionbombardment of the fragmented species of feed gas (e.g., acetylene) andions of carrier gas (e.g., argon) onto the substrate to cause atomicarrangement/rearrangement of the coating being formed to a densestructure. Simultaneously, the cathode is utilized for extensivefragmentation of the feed gas, as described in U.S. Pat. No. 4,382,100(Holland). Because the two process parameters, namely the extensivefragmentation and the ion attraction cannot be controlled independently,conventional PECVD methods are limited and unfavorable for high ratedeposition. This limitation has been overcome in U.S. Pat. No. 5,464,667(Kohler et al.), which teaches the independent use of the hollow cathodefor feed gas fragmentation and a second cathode to bias the filmsubstrate to deposit these fragments.

[0036] The present invention includes modifications of the systemsdescribed in U.S. Pat. Nos. 5,286,534 (Kohler et al.) and 5,464,667(Kohler et al.), which allow for the deposition of dense coatingswithout extensive fragmentation of the starting material. Significantly,using the process and system of the present invention, high molecularweight organic starting materials can be converted into dense coatingswithout extensive fragmentation and without a significant loss ofphysical and chemical properties inherent to the starting material.These differences between the coatings of the present invention andcoatings produced by conventional methods are exemplified by Examples 1,3, and 4 and Comparative Example A discussed in greater detail below.

[0037] The plasma is generated from a plasma gas using a hollow cathodesystem, such as a “hollow cathode tube” (as disclosed in U.S. Pat. No.5,286,534 (Kohler et al.)) or a “hollow cathode slot” (as disclosed inU.S. Pat. No. 5,464,667 (Kohler et al.)), preferably a slot comprisingtwo electrode plates arranged parallel to each other, and morepreferably, a tube in line with a slot, and then directed toward andtypically past an anode (as described in U.S. Pat. No. 5,464,667 (Kohleret al.)). In one preferred embodiment, the hollow cathode slot systemincludes a first component having therein a hollow cathode tube, asecond compartment connected to the first compartment, and a thirdcompartment connected to the second compartment having therein the twoparallel plates. Alternatively, a system referred to herein as a “pointsource” can also be used as the hollow cathode system to generate aplasma. These all form a jet plasma within the hollow cathode, which ispropelled past or toward an anode. This is in contrast to conventional“plasma jet” systems in which the plasma is generated between thecathode and anode and a jet stream is directed out of the cathode/anodearrangement.

[0038] The plasma gas includes a carrier gas, such as argon. andoptionally a feed gas. The feed gas can be any suitable source for thedesired composition of the coating. Typically, the feed gas is a sourcefor a carbon-rich coating. The feed gas is preferably selected from thegroup consisting of saturated and unsaturated hydrocarbons,nitrogen-containing hydrocarbons, oxygen-containing hydrocarbons,halogen-containing hydrocarbons, and silicon-containing hydrocarbons.The vaporized organic material (preferably a vaporized organic liquid)is typically used to provide other materials that form uniformmulti-component or multilayer coatings, although the plasma gas couldalso be the source of such components. That is, a low molecular weightsilicon-containing compound could be used to generate a plasma.

[0039] Referring to FIG. 1, a particularly preferred jet plasmaapparatus for deposition of such coatings is shown. This apparatus issimilar to that shown in U.S. Pat. No. 5,464,667 (Kohler et al.)modified for the deposition of two materials either simultaneously orsequentially. The apparatus includes feed gas source 20 and carrier gassource 22 connected via flow controllers 24 and 25, respectively, toinlet tubes 26 and 27, respectively. Carrier gas, e.g., argon, from thegas source 22 is fed into a vacuum chamber 30 and into a hollow cathodesystem 40 through an inlet port 28. Feed gas, e.g., acetylene, from thegas source 20 is fed into the vacuum chamber 30 and into the hollowcathode system 40 through an inlet port 29. The hollow cathode system 40shown in FIG. 1 is divided into three compartments, i.e., a firstcompartment 41, a second compartment 42, and a third compartment 43. Thecarrier gas, if used, is fed into the first compartment 41, whereas thefeed gas is fed into the second compartment 42. A plasma can be formedfrom the carrier gas in the first compartment and/or from the carrierand feed gases in the third compartment. This hollow cathode system isfurther discussed in U.S. Pat. No. 5,464,667 (Kohler et al.), thediscussion of which is incorporated herein by reference.

[0040] In addition to the hollow cathode system 40, inside the vacuumchamber 30 is an anode system 60, which may be either grounded orungrounded, and which preferably contains an adjustable shield 61. Alsoincluded are a radio frequency bias electrode 70, a substrate (e.g.,polyethylene terephthalate “PET” film) 75, and an oil delivery system120. The oil delivery system 120 provides a vaporized organic liquid fordeposition on the substrate. It includes oil reservoir 122, coolingsystem 123, oil delivery system 124, evaporator chamber 126, outlet port128, adjustable divider plate 130, and substrate protecting shield 129.The divider plate 130 is used to keep the plasma and vaporized liquidseparate until they are close to the substrate. The substrate protectingshield 129 is used to avoid the condensation of vaporized liquid ontothe nonbiased substrate. Both the divider plate 130 and the substrateprotecting shield 129 are optional.

[0041] The substrate 75 is generally unwound from a first roll 76 and isrewound upon a second roll 78, although it can be a continuous loop ofmaterial. The plasma gas, i.e., feed gas alone or mixture of feed gasand carrier gas, is converted into a plasma within the hollow cathodesystem 40. The plasma 160 is then directed toward the substrate 75,which preferably contacts the radio frequency bias electrode 70 duringdeposition of the coating from the plasma. The substrate can be made ofa wide variety of materials. For example, it can be a polymeric,metallic, or ceramic substrate. In a preferred embodiment, the substrateis a thin, i.e., less than 0.05 cm, and flexible polymeric film.Examples of useful films are oriented polyester, nylon, biaxiallyoriented polypropylene, and the like.

[0042] The radio frequency bias electrode 70 is made of metal, such ascopper, steel, stainless steel, etc., and is preferably in the form of aroll, although this is not necessarily a requirement. For example, itcan be in the form of a plate. The roll is advantageous, however,because it reduces friction between the electrode and the substrate,thereby reducing film distortion. More preferably, the radio frequencybias electrode 70 is water-cooled to a temperature no greater than aboutroom temperature (i.e., about 25° C. to about 30° C.), preferably to atemperature of about 0° C. to about 5° C., which is advantageous whenheat-sensitive substrates are used. The radio frequency bias electrodetypically has a frequency of about 25 KHz to about 400 KHz, although itis possible to increase the frequency range up to and including themegahertz range. It typically has a bias voltage of about minus 100volts to about minus 1500 volts. With the bias voltage applied, anadditional plasma is created in the proximity of the radio frequencybias electrode 70 that generates a negative potential at the substrate,and attracts the plasma species 160 toward the substrate 75 forefficient and rapid deposition.

[0043] To create a plasma, a first DC power supply 80 is electricallyconnected directly to the first compartment 41 of the hollow cathodesystem 40 by a circuit 82 and to the anode system 60 by a circuit 84.The first DC power supply 80 can be a pulsating DC power supply, afiltered DC power supply, or other plasma-generating means withappropriate arc suppression, such as those used in sputtering systems.An unfiltered pulsating DC power supply is generally preferred, however.Also, a second DC power supply 85 is electrically connected directly tothe third compartment 43 of the hollow cathode system 40 by a circuit 87and to the anode system 60 also by circuit 84. In this arrangementchamber 41 and chamber 43 are electrically isolated from each other. Thesecond DC power supply 85 can be a pulsating DC power supply, a filteredDC power supply, or other plasma-generating means with appropriate arcsuppression, although a pulsating DC power supply is preferred. Anexample of a filtered DC power supply is a 25 kilowatt filtered DC powersupply, such as that available from Hippotronics Inc., New York, N.Y.Such a power supply generates a plasma at high currents up to about 10amperes, and relatively low voltage, i.e., about minus 100 volts.

[0044] A radio frequency biasing power supply 90 (e.g., PLASMALOC 3power supply from ENI Power Systems, Inc., Rochester, N.Y.) is connectedto the radio frequency bias electrode 70 by a circuit 92 and to a ground100 by a circuit 94. The DC power supplies 80 and 85 can also beconnected to the ground 100, although this is not a preferredarrangement. This electrical connection is represented in FIG. 1 by thedashed line 105. Thus, in this arrangement wherein all three powersupplies are attached to ground 100, the anode system 60 is grounded.The former arrangement, wherein the anode system 60 is not grounded, isadvantageous when compared to the latter arrangement. For example, whenthe anode system 60 is not grounded, the plasma formed is more stable,because the plasma sees the anode system as distinct from the groundedmetal chamber. Typically, when the anode system 60 is not grounded, thecross-web coating thickness, i.e., the coating thickness along the widthof the substrate, is more uniform. Furthermore, the plasma is moreconfined and the pattern of deposition can be more readily controlled byvarying the exposure of the plasma to the anode system 60.

[0045] As stated above, DC power supplies 80 and 85 are preferablypulsating DC power supplies. This is because pulsating DC power suppliesprovide more stable plasma conditions than nonpulsating DC powersupplies, which contributes to uniform plasma deposition rates andtherefore down-web, i.e., along the length of the substrate, coatinguniformity. Furthermore, they allow for the use of high current flow,and thus high deposition rates, at relatively low voltage.

[0046] Whether used as the first DC power supply 80 or the second DCpower supply 85, or both, a preferred pulsating DC power supply is onethat provides a voltage that typically passes through zero about 25times/second to about 1000 times/second, more preferably about 25times/second to about 200 times/second, and most preferably about 100times/second to about 120 times/second. This allows the plasma toextinguish and then reignite as the cathode reaches its necessarypotential. Examples of such pulsating DC power supplies include theAirco Temescal Model CL-2A power supply with a 500 mA maximum output anda 120 Hz full-wave rectified DC voltage from 0 volts to minus 5000volts, available from Airco Temescal, Berkeley, Calif. Another versionof this power supply uses two Airco Temescal transformers in parallel,thereby resulting in a 1 ampere maximum output. These pulsating DC powersupplies were used in the examples described below. Another power supplywas built with a 20 ampere maximum output, and also used in the examplesdescribed below. This was accomplished with a larger size (1 kilowatt),leakage-type transformer obtained from MAG-CON Inc., Roseville, Minn.,including full wave rectification to achieve pulsating DC output. Asused herein, a “leakage-type” transformer is one that provides a stableoperating point for a load with a negative dynamic resistance. Typicaloutput of this 20 ampere power supply is 0 volts direct current (VDC) tominus 1500 VDC with current of 0 ampere to 20 amperes. This power supplyis current limited, which prevents formation of high intensity arcs atthe cathode surfaces. If greater currents are required, a largerleakage-type transformer can be used, or two or more smallertransformers can be arranged in parallel.

[0047] In particularly preferred embodiments of the present invention,both power supply 80 and power supply 85 are pulsating DC powersupplies. In such embodiments, a carrier gas is injected into the firstcompartment 41 of the hollow cathode system 40 and a pulsating DC powersupply, preferably a 500 mA pulsating DC power supply, is used to createa plasma from the carrier gas. Although formation of this initialcarrier gas plasma may not always be necessary when a pulsating DC powersupply is used to generate a plasma in the third compartment 43 of thehollow cathode system 40, it is necessary for ignition of a plasma inthe third compartment when a nonpulsating filtered DC power supply isused. After initial ignition of the carrier gas plasma in particularlypreferred embodiments of the present invention, this initial plasmapasses into the second compartment 42 of the hollow cathode system 40where it is mixed with the feed gas. This mixture then passes into thethird compartment 43 where a second plasma is created using a pulsatingDC power supply. This pulsating DC power supply can be a 1 ampere or 20ampere power supply, as used in the examples, or it can be a 500 mApower supply or a 20 ampere, 30 ampere, 50 ampere, 100 ampere, etc.,power supply, depending on the desired feed gas fragment concentrationand coating deposition rate.

[0048] In the first compartment 41 of the hollow cathode system 40, suchas a hollow cathode slot system, the voltage created and maintained ispreferably about minus 200 volts to about minus 1000 volts, preferablyabout minus 200 volts to about minus 500 volts. The power supplied tothis first compartment is typically about 20 watts to about 10,000watts, preferably about 20 watts to about 1000 watts, and morepreferably about 100 watts to about 500 watts. In the third compartment43 of the hollow cathode system 40, the voltage created and maintainedis preferably about minus 50 volts to about minus 500 volts, and morepreferably about minus 80 volts to about minus 120 volts. The powersupplied to this second compartment is typically about 50 watts to about3000 watts, and more preferably about 1000 watts to about 3000 watts.

[0049] Given the correct conditions, a stable jet plasma 160 is formedin the vacuum chamber which spreads out in an extended pattern generallyimaging the shape of the exit slot of the hollow cathode system 40.Preferred plasmas have a high feed gas fragment concentration, i.e.,fragmentation of the feed gas occurs at a high rate, so as to provide arapid deposition rate of the carbon-rich coating on the substrate 75.That is, the higher the deposition rate of a coating and the moreuniform the coating, the more desirable the plasma formed, which dependson the system arrangement and the current and voltage provided.Furthermore, if a highly uniform coating can be deposited at arelatively high rate with low power requirements, the more desirable thesystem with respect to practical considerations (e.g., cost, safety, andpreventing overheating).

[0050] To monitor the conditions in the vacuum chamber, a variety ofinstruments, such as a mass spectrometer, an emission spectrometer, anda capacitance manometer, can be connected to the vacuum chamber. Avacuum can be created and maintained within the vacuum chamber by anymeans typically used to create a vacuum (e.g., diffusion pump and/ormechanical pump). The vacuum chamber is typically maintained at apressure of about 0.13 Pascals (Pa) to about 130 Pa, preferably at about0.13 Pa to about 1.0 Pa. It will be understood by one skilled in the artthat the method and apparatus described herein can be used in anaturally occurring vacuum, such as occurs in space.

[0051] In order to deliver liquids in vapor form into vacuum chamber 30,oil delivery system 120 is used to control oil feed rate- forevaporation. As shown in FIG. 1, oil 121 is delivered from a reservoir122 placed in vacuum chamber 30, through oil delivery orifice 124. Thisdelivers the oil into evaporator 126 for evaporation and out evaporatoroutlet port 128 for delivery to the radio frequency bias electrode 70.Valve system 140 is used to expose oil 121 to the vacuum so as to becomede-aerated. During this de-aeration process, oil discharge through oildelivery orifice 124 is prevented by having equal pressure above theliquid (e.g. oil 121) and at the oil delivery orifice 124. Theconfiguration of valve system 140 is changed to introduce air intoreservoir 122 in the space above oil 121 to impose a desirable pressureabove the oil. Typically, the oil delivery orifice 124 is a tube orneedle, such as a syringe needle, although other delivery orifices ofother shapes could be used. The oil feed rate is controlled by properselection of the temperature of the delivery means, which controls theviscosity, and the size of the delivery means, which controls the massflow rate. Depending on the desired result, oil feed rate can be variedover a broad range. The temperature of the oil delivery orifice 124 canbe regulated by cooling system 123. This can be a liquid-. gas-, orelectric-cooled system. The temperature of the oil delivery orifice 124and the evaporator 126 can be monitored using a thermocouple, forexample.

[0052]FIG. 1 also shows divider plate 130 and substrate protectionshield 129. Typically, these components are made of quartz, although anymaterial can be used, such as metal, plastic, or ceramic, as long as itcan withstand the temperatures experienced in the system duringdeposition. As stated above, these components are optional.

[0053] Oil delivery system 120 is shown in greater detail in FIG. 2,along with valve system 140. The oil delivery system 120 includes an oilreservoir 122 and a flash evaporator 126 consisting of one or morespacers 127 made of a thermally conductive material (e.g., aluminum).The spacers 127 can be heated by any of a variety of means, such asvariac-controlled cartridge type resistance heaters (not shown in FIG.2). A cooling system 123, such as a water-cooled copper sleeve, thataccommodates the oil delivery orifice 124 (e.g., a needle) is placedinto an inlet port 125 of the flash evaporator 126. The inlet port 125is preferably situated at the back region of the flash evaporator 126and preferably includes a sleeve insert, such as a silicone rubbersleeve insert, to prevent heat exchange between the flash evaporator 126and the cooling system 123. The tip of the oil delivery orifice 124(e.g., needle), however, is in immediate contact with the heated inletport 125 allowing constant and uniform vaporization of the oil. Theindividually shaped spacers 127 preferably provide multiple spacings sothat the vaporized oil is guided over the full width of the flashevaporator 126 several times upwards and downwards (as shown by thedotted line) before the vapor is discharged uniformly through an outletport 128 into the vacuum chamber (not shown in FIG. 2).

[0054] An atomizer can also be used to atomize the organic material(i.e., form liquid droplets of the material) prior to vaporizing theorganic material. The atomizer is particularly necessary for organicmaterials that are unsaturated, although it can also be used withsaturated organic materials. This is particularly true if extendedperiods of vaporization are used (e.g., greater than a few minutes)because this can clog the orifice of the evaporator. A system thatincludes an atomizer is shown in FIG. 3, wherein oil delivery system 220is shown in greater detail along with valve system 140. In thisembodiment, the oil delivery system 220 includes an oil reservoir 222, aflash evaporator 226 consisting of one or more spacers 227, a coolingsystem 223, oil delivery orifice 224, inlet port 225 in the flashevaporator 226, and an outlet port 228 as described with respect to FIG.2. Also included to atomize the organic material is an ultrasonic horn230 attached to an ultrasonic converter 229, as is known in the art. Auseful ultrasonic system is a Branson VC54 unit (40 kHz, available fromSonics and Materials, Inc., Danbury, Conn.), tuned to provide maximumatomization. Other means by which the organic material can be atomizedare described, for example, in U.S. Pat. No. 4,954,371.

[0055] An alternative jet plasma vapor deposition apparatus 300 is shownin FIG. 4. This system includes a radio frequency bias electrode 310(also referred to herein as a biased chill roll or simply a chill roll)with a portion of the radio frequency bias electrode 310 preferablycovered by a dark space ground shield 312, such as an aluminum sheet, toform a discrete deposition area 314. Preferably, at least about 76% ofthe surface of the radio frequency bias electrode 310 is covered by darkspace ground shield 312. Dark space ground shield 312 is grounded andplaced about 0.3 centimeter (cm) to about 2.5 cm away from the surfaceof radio frequency bias electrode 310 to provide a dark space and thusconcentrate the bias wattage over the exposed surface area of radiofrequency bias electrode 310.

[0056] The jet plasma vapor deposition apparatus 300 of FIG. 4 alsoincludes a hollow cathode system 315, which includes a point sourcecathode 316, a feed gas source 317 and a carrier gas source 318, forgenerating a plasma, an oil delivery system 320, attached to a valvesystem 321, and an anode system 322 (e.g., an anode wire as describedherein). In this arrangement, the oil delivery system 320 and attachedvalve system 321 are optional. In the specific embodiment shown in FIG.4, an imaginary horizontal plane can be drawn from the center of theradio frequency bias electrode 310 to the slot opening of the optionaloil delivery system 320, dividing the noncovered surface area (i.e., thedeposition area 314) in half. The point source cathode 316 is placedabove the imaginary plane and the anode system 322 is placed below theimaginary plane. Plasma extends as a point source from the point sourcecathode 316 into the vacuum in a cone shape configuration concentratingnear the radio frequency bias electrode 310 and at the anode wire 322.Although FIG. 4 is not too scale, in one embodiment of this system, thepoint source cathode 316 is placed about 7.5 cm above the imaginaryplane and about 7.5 cm away from the surface of the radio frequency biaselectrode 310. It is tilted from its horizontal position by about 60° toensure a downward expansion of the plasma toward the anode wire 322 andthe deposition area. The anode wire 322 is placed about 17.5 cm belowthe imaginary plane and about 5 cm away from the radio frequency biaselectrode 310. The dark space ground shield 312 prevents the anode wire322 from being in-line-of-sight with the deposition area. Thesedistances, lengths, angles, and other dimensions are presented asexemplary only. They are not intended to be limiting.

[0057] Referring to FIG. 5, a point source cathode 400 is shown, whichenables the generation of a plasma from a small orifice 403 of ahollowed cylinder 402, which is surrounded by a magnet 408, preferably acircular magnet, and equipped with an electrode, such as thespherical-H.V. electrode 410. The cathode 400 preferably includes awater-cooled cylinder 402, which is typically made of copper, althoughit can be made of graphite or other electrically and thermallyconductive metals. A tube 404, preferably having a circular crosssection, is inserted inside a bore 406 of the cylinder 402 having theleading edge 405 recessed within the bore 406 of the cylinder 402 suchthat it is in the plane of the center line of a circular magnet 408 thatsurrounds the cylinder 402 at its outlet end. The tube 404 is preferablyceramic, although it can be made of other materials that withstand hightemperatures and are electrical insulators. The external surfaces of thecylinder 402 can be shielded with quartz 412 (as by the use of a quartzsleeve) to avoid plasma arcing. This arrangement can be better seen inFIG. 5A, which is a cross section of the point source cathode 400 takenalong line A-A, which also shows a water inlet 417 and water outlet 418.

[0058] Using this particular configuration, a stable plasma can besustained and contained in region 414 defined by extensions 416 of thecylinder 402. This configuration of the cylinder 402 along with theplacement of the magnet 408 concentrates the plasma such that it extendsas a point source into the vacuum in a cone shape configuration. It isimportant to note that the strongest plasma is generated if the leadingedge 405 of the ceramic tube 404 is directly in line with the center(with respect to its width) of the circular magnet 408. Also, themagnetic field flux density is preferably at least about 0.15 Kgauss,and more preferably, at least about 1.5 Kgauss. The magnet 408 ispreferably made of a ceramic material, although metallic alloys can beused. Ceramic materials generally have better temperature stability anda higher Curie point (i.e., the point at which magnetism is lost), andare therefore preferred.

[0059] Particularly preferred embodiments of the present inventioninclude an anode system (60 in FIG. 1 or 322 in FIG. 4), preferably anadjustable anode system as shown in FIG. 4 of U.S. Pat. No. 5,464,667(Kohler et al.). The anode system, particularly the adjustable anodesystem, contributes to the maintenance of a stable plasma, and to theuniformity of the coatings. In a preferred embodiment of the anodesystem used herein, however, the enclosing glass box described in U.S.Pat. No. 5,464,667 (Kohler et al.) is omitted. Typically and preferably,two tungsten wires function as the anodes. Each wire is of a sufficientdiameter to provide the temperature desired, and of a sufficient lengthto provide the coating width desired. Typically, for a temperature ofabout 800° C. to about 1100° C., two tungsten wires of about 0.1 cm toabout 0.3 cm in diameter function effectively as anodes with 10 amperesto 20 amperes of electron current sustained from the plasma. Portions ofthe wires can be covered as described in U.S. Pat. No. 5,464.667 (Kohleret al.). Again, the wire diameter and length are presented as exemplaryonly. They are not intended to be limiting. Any anode can be used aslong as the plasma is generated in the cathode and directed toward andpast the anode.

[0060] It is to be understood that one or more additionalevaporators/hollow cathode tubes, slots, or point systems that generateplasmas as described herein may also be included within the systems ofthe present invention. The multiple systems can provide more than onelayer onto the substrate or can provide an increased rate of deposition.

[0061] The processes and systems of the present invention can be used toprepare any of a variety of carbon-containing and/or silicon-containingcoatings, such as amorphous highly dense coatings, layered coatings, anduniform multi-component coatings, and the like.

[0062] The composition of the coatings can be controlled by means of theconcentration and composition of the feed gas passed through the hollowcathode, and the organic material vaporized in the evaporator. Thedensity of the coatings are controlled by means of the chamber pressure,the electrical power (current and voltage) supplied by the DC and radiofrequency power supplies. The conditions for the formation of highdensity coatings are generally chosen to balance the bias power to theconcentration of the starting material. That is, the specific powerdensity includes bias power density, reaction time, and concentration ofstarting material. Generally, the specific power density is increased byhigher power density and longer reaction time, and decreased byincreased concentration of the starting material. Generally, the higherthe power density, the more dense the coating.

[0063] The bias power density typically varies from about 0.1 watt/cm²to about 10 watts/cm² (preferably, about 0.5 watt/cm² to about 5watts/cm²). The bias voltage typically varies from about minus 50 voltsto about minus 2000 volts (preferably, about minus 100 volts to aboutminus 1000 volts). The bias current density typically varies from about0.1 mAmp/cm² to about 50 mAmps/cm² (preferably, about 1 mAmp/cm² toabout 5 mAmps/cm²). The jet plasma voltage typically varies from aboutminus 50 volts to about minus 150 volts (preferably, about minus 80volts to about minus 100 volts). The jet plasma current typically is atleast about 0.1 Amp (preferably, at least about 0.5 Amp). The upperlimit of the jet plasma current is typically dictated by the limitationof the power supply.

[0064] The chamber pressure is typically less than about 1 Torr (130Pa). Preferably, the pressure in the reaction chamber is less than about8 milliTorr (1.0 Pa). Generally, the less the pressure (i.e., the higherthe vacuum), the more dense the coating. The web speed of the substrate(i.e., the coating rate) typically varies from about 1 foot/minute toabout 1000 feet/minute (0.3 meter/minute to about 300 meters/minute).Preferably, the web speed is about 0.9 meter/minute to about 6meters/minute. The reaction time typically varies from about 0.01 secondto about 10 seconds, and preferably, from about 0.1 second to about 1second.

[0065] As discussed below and shown in FIG. 6, the application of highbias power is a factor for obtaining excellent barrier properties. Inorder to achieve high bias wattage, the hollow cathode is typicallypositioned in line-of-sight of the film substrate/chill roll. Thisarrangement makes possible satisfactory interaction of the jet plasmawith the biased film substrate. In the absence of the plasma, thewattage power that can be applied is significantly reduced. When the jetplasma stream is shielded from the biased film substrate, the bias poweris also reduced. This indicates the necessity for a specific apparatusarrangement to maximize jet plasma flow toward the biased filmsubstrate. Preferably, the jet plasma system provides both confinementand directionality of the plasma. Conventional systems utilizing plasmasources other than the point source of the present invention and thosedescribed in U.S. Pat. Nos. 5,232,791 (Kohler et al.), 5,286,534 (Kohleret al.), and 5,464,667 (Kohler et al.) lack the combination ofconfinement and directionality. Thus, preferred systems of the presentinvention are improved with respect to these parameters.

[0066] As stated previously, the plasma is created from a carrier gas ora mixture of a carrier gas and a feed gas. This is referred to herein asthe “plasma gas.” The carrier gas flow rate can be about 50 standardcubic centimeters per minute (sccm) to about 500 sccm, preferably about50 sccm to about 100 sccm, and the feed gas flow rate can be about 100sccm to about 60,000 sccm, preferably about 300 sccm to about 2000 sccm.For example, for carbon deposition rates of about 20 Å/second to about800 Å/second, the feed gas flow rate is about 50 sccm to about 350 sccmand the carrier gas flow rate is about 50 sccm to about 100 sccm, withhigher feed gas flow rates in combination with lower carrier gas flowrates (typically resulting in higher deposition rates). Generally, forharder coatings, the carrier gas flow rate is increased and the feed gasflow rate is decreased.

[0067] The feed gas, i.e., the carbon source, can be any of a variety ofsaturated or unsaturated hydrocarbon gases. Such gases can also contain,for example, nitrogen, oxygen, halides, and silicon. Examples ofsuitable feed gases include, but are not limited to: saturated andunsaturated hydrocarbons such as methane, ethane, ethylene, acetylene,and butadiene; nitrogen-containing hydrocarbons such as methylamine andmethylcyanide; oxygen-containing hydrocarbons such as methyl alcohol andacetone; halogen-containing hydrocarbons such as methyl iodide andmethyl bromide; and silicon-containing hydrocarbons such astetramethylsilane, chlorotrimethyl silane, and tetramethoxysilane. Thefeed gas can be gaseous at the temperature and pressure of use, or itcan be an easily volatilized liquid. A particularly preferred feed gasis acetylene.

[0068] As stated previously, a carrier gas can also be used with thefeed gas to advantage. For example, without the auxiliary plasma fromthe carrier gas the feed gas plasma is difficult to sustain at aroundminus 100 volts using either a pulsating or a filtered DC power supply.For example, when using only the feed gas, with a 1 ampere pulsating DCpower supply the voltage rises occasionally up to about minus 1000volts, and with a nonpulsating filtered 10 ampere power supply, theplasma is occasionally extinguished altogether.

[0069] The carrier gas can be any inert gas, i.e., a gas that isgenerally unreactive with the chosen feed gas under the conditions ofpressure and temperature of the process of the present invention.Suitable carrier gases include, but are not limited to, helium, neon,argon, krypton, and nitrogen. Typically, higher weight gases, e.g.,argon, are preferred. The terms “inert” and “carrier” are not meant toimply that such gases do not take part in the deposition process at all.

[0070] The thickness of coatings produced by the method of the presentinvention are typically greater than about 5 nanometers (nm), preferablyabout 10 nm to about 1000 nm, however, thicker coatings are possible,but not typically needed. The substrate moves through the plasma at arate designed to provide a coating of a desired thickness. Referring toFIG. 1, the speed at which the substrate 75 travels from roll 76 to roll78 can be about 10 mm/second to about 4000 mm/second, but is typicallyabout 10 mm/second to about 1500 mm/second for the gas flow rates andpressures and the apparatus described above.

EXAMPLES

[0071] The present invention is further described by the followingnonlimiting examples. These examples are offered to further illustratethe various specific and preferred embodiments and techniques. It shouldbe understood, however, that many variations and modifications can bemade while remaining within the scope of the present invention.

[0072] Test Procedures

[0073] A brief description of the tests utilized in some or all of thefollowing examples will now be given.

[0074] Water vapor permeability of the coatings was measured with aPermatran W6 Permeability Tester manufactured by Modem Controls, Inc.,Minneapolis, Minn. The ASTM test method F 1249-90 included aluminum foiland PET film for standard calibration, sample conditioning overnight,cell filled halfway with deionized water and 60 minute test with anitrogen gas pressure of 15 psi (1.0×10⁵ Pascals).

[0075] Abrasion resistance was measured by a combination of two ASTMtest methods. The Taber Abrasion Test, ASTM D4060-95 was used with a“TABER” Abraser Model 503 with “CALIBRASE” CS-10F wheels (TeledyneTaber, North Tonawanda, N.Y.). A 500 g total weight load evenlydistributed on the two CS-10F wheels was used. The cycles were variedbetween 0 and 100 cycles. The second test method was ASTM D1003 whichused a Gardener Hazemeter, “HAZEGARD” System, Model XL211 (PacificScientific, Gardner/Neotac Instrument Division, Silver Spring, Md.). Inthis method the percentage of light scattering was measured before andafter the specimen was Taber abraded. The lower the value, the betterthe abrasion resistance and hardness.

[0076] Adhesion was measured by the 90° angle peel adhesion method. Theuncoated side of the film samples was affixed via double sided adhesivetape to a stainless steel panel. Usually, an aggressive, silicone basedpressure sensitive adhesive tape was affixed to the coated side using aseven pound roller, rolled two times each direction over the tape. Thespecimens were 1.27 cm wide and about 30.5 cm long. The silicone basedtape was removed from the coating at a speed of twelve inches per minutein a 90° peel using an Instron Instrument, Model 1122.

[0077] Hardness was measured by an ultramicro hardness tester UMIS 2000from CSIRO (Australia). The indentation method included a Berkovichindenter with a 65° cone angle. The indenter was made from diamond. Thehardness values were determined by the analysis of the loading-unloadingdata.

[0078] Density was measured by the floating method. Powdered sampleswere suspended in liquids of varying density and the movement of thesuspended particles were observed. Upward movement indicated that theparticles were less dense than the liquid; downward movement indicatedthat the particles were more dense than the liquid. No movementindicated identical densities. Final readings were made after twelvehours when the particles usually had risen to the top of the liquid orsettled at the bottom. Using liquids with incremental differences indensity, the density of the particles could be bracketed. The liquidswith varying densities used are listed in Table 1. TABLE 1 LiquidDensity (g/cm³) 1-bromoheptane 1.14 2-bromopropane 1.311-bromo-2-fluorobenzene 1.601 4-bromoveratrole 1.702

[0079] Thickness and uniformity of the jet plasma coatings on filmsubstrates were assessed from the interference color produced by thecoatings on silicone wafers. Small pieces of silicone wafers werepositioned at strategic locations on the film substrate prior todeposition of the coatings. Such a method was suitable for coatingshaving thicknesses up to about 1500 Å. For greater coating thicknesses astep profilometer was used, manufactured by Tencor Instruments, MountainView, Calif. The instrument measured the step formed by the coating andthe adjacent uncoated area which was masked by adhesive tape duringdeposition.

[0080] Along with the determination of the index of refraction,thickness of the coatings was also determined from ellipsometric valuesobtained from the coatings on silicon wafers. The measurements were madeon an ellipsometer Model 116B, manufactured by Gaertener ScientificCorporation, Chicago, Ill.

[0081] Static coefficient of friction was measured by the Inclined PlaneMethod. The sample, typically about 2 cm wide and 5 cm long, wasfastened on a horizontal plane which could be inclined. The free ends ofa U shaped steel wire (1 mm in diameter) were attached to stabilizingarms. The rounded end of the U shaped wire (paper clip like) was placedupright and in a self-supporting manner onto the sample surface. Theinclined plane was raised until sliding of the U shaped steel wirebegan. The static coefficient of friction was equal to the tangent ofthe angle at which sliding began.

EXAMPLE 1

[0082] Silicone coatings were deposited on 30 cm wide and 0.074 mm thickuntreated polyethylene terephthalate (PET) in the system show in FIG. 4.The system is similar to the deposition chamber described in U.S. Pat.No. 5,464,667 (Kohler et al.) with several modifications, including apoint source cathode and an oil delivery system.

[0083] The system included a biased chill roll, 48.2 cm in diameter and33.5 cm wide. Except for the deposition area, about 76% of the surfaceof the radio frequency bias electrode was covered by an aluminum sheet.The aluminum sheet was grounded and placed about 0.6 cm away from thesurface to provide a dark space and thus concentrated the bias wattageover the remaining 24% of the surface area. An imaginary horizontalplane could be drawn from the center of the radio frequency biaselectrode to the slot opening of the oil delivery system, dividing thenoncovered surface area in half. The point source cathode was placedabout 7.5 cm above the imaginary plane and about 7.5 cm away from theradio frequency bias electrode surface. The point source cathode wasmachined in the form of a hollowed cylinder and tilted from itshorizontal position by about 60° to ensure a downward expansion of theplasma toward the anode wire and the deposition area. The anode wire wasplaced about 17.5 cm below the imaginary plane and about 5 cm away fromthe chill roll. The grounded aluminum sheet prevented the anode wirefrom being in-line-of-sight with the deposition area.

[0084] In contrast to the hollow cathode slot of U.S. Pat. No. 5,464,667(Kohler et al.), a hollow cathode point source was used which enabledthe generation of a plasma from a small orifice. As shown in FIG. 5, thecathode consisted of a water-cooled copper cylinder, 5 cm long. Aceramic tube was inserted into the bore of the cylinder with the tiprecessed to be in the plane of the center line of the magnet. The boreof the ceramic tube was 0.35 cm. The circular ceramic magnet was placedas shown in FIG. 5 at the front end of the cathode, 5.0 cm in outerdiameter and 2.0 cm in inner diameter. The magnetic flux density at thecenter of the magnet was measured to be 0.45 Kgauss. The externalsurfaces of the cathode were covered with 0.3 cm thick quartz to avoidplasma arcing. A stable plasma was sustained with 150 sccm argonextending as a point source from the tip of the cathode into the vacuumand concentrating near the radio frequency bias electrode and at theanode wire.

[0085] The anode was similar to that shown in FIG. 4 of U.S. Pat. No.5,464,667 (Kohler et al.) except the enclosing glass box was omitted.Two tungsten wires each 0.1 cm diameter and 40 cm long functioned asanodes that reached a temperature of 800-100° C. with 10-20 amperes ofelectric current sustained from the plasma. The midsection of thetungsten wires were covered with quartz tubing.

[0086] In order to deliver liquids in vapor form into the vacuum chamberan oil delivery system was developed to control oil feed rate and thusoil evaporation. This is shown in FIGS. 1 and 4, and in greater detailin FIGS. 2 and 3. With the valve configuration shown in FIGS. 2 and 3,the oil was exposed to the vacuum so as to become de-aerated. This wasdone by first evacuating chamber 30 (FIG. 1) and then opening valves V1and V2 and closing valve V4, with valve V3 set at the desired meteringrate. The chamber was allowed to stabilize and the oil was outgasseduntil all residual gases were boiled off. Oil discharge through the oildelivery needle was prevented by having equal pressure above the liquidand at the needle. By changing the valve configuration, such that valveVI was closed and valves V2, V3, and V4 were opened, air was introducedinto the space above the oil. Valve V3, a flow-metering valve, wasadjusted to control the pressure to impose a desirable pressure abovethe oil, as measured by vacuum gauge 141. Once the desirable pressurewas reached, valve V2 was closed. In addition, oil feed rate wascontrolled by proper selection of the gauge and the temperature of theneedle. The needle temperature was regulated by an attachedwater-temperature controlled copper sleeve.

[0087] As shown in FIG. 2 the evaporator consisted of multiple aluminumspacers that were heated by two variac-controlled cartridge typeresistance heaters. The copper sleeve accommodating the oil deliveryneedle was placed into the inlet port of the heater. The inlet port wassituated at the back region of the heater and was filled with a siliconerubber sleeve insert to prevent heat exchange between the heater and thecopper sleeve. The tip of the needle, however, was in immediate contactwith the heated inlet port allowing constant and uniform vaporization ofthe oil. The individually shaped aluminum spacers provided multiplespacings so that the vaporized oil was guided over the full width of theheater several times upwards and downwards before the vapor wasdischarged uniformly through a slot into the vacuum chamber as shown inFIG. 1.

[0088] The cathodic point source was powered by a 20 ampere maximumoutput pulsating DC power supply as described in U.S. Pat. No. 5,464,667(Kohler et al.). The Airco Temescal CL-2A power supply consists of aleakage type power transformer that supplies AC power to a full wavebridge rectifier to yield- an output, which is the absolute value of thetransformer output voltage, i.e., the negative absolute value of a sinewave starting at zero volts and going to a peak negative value of about5000 volts open circuit. Under a purely resistive load of 100 ohms, thispower supply would rise to a voltage of minus 200 volts with the currentlimited at 500 mA. With an arc plasma as a load, the output voltage ofthe power supply climbs to the breakdown voltage of the apparatus andthen the voltage drops immediately to the arc steady state voltage withcurrent limited to 500 mA. Thus, the leakage transformer employed actsto limit current flow through the load or plasma in a manner similar toa resistive ballast in a typical glow discharge system. Morespecifically, as the cycle of power supply output voltage (starting atT₀) progresses through the 120 Hz waveform (starting at zero outputvolts), the voltage increases with time to a negative voltage valuesignificantly above the arc steady state voltage. At this point, voltagebreakdown occurs in the plasma jet, an arc is established, and the powersupply output drops to the arc steady state voltage of about minus 100volts and the saturation current of the power transformer, about 500 mAfor the CL-2A power supply. As time progresses through the cycle, thepower supply voltage drops below the arc voltage and the arcextinguishes. The power supply output voltage continues to drop,reaching zero volts at T₀+{fraction (1/120)} second and the processstarts again. The time period for this entire cycle is {fraction(1/120)}of a second, or twice the frequency of the AC line input voltageto the power supply. The operations of the 1 amp power supply and the 20amp power supply are identical except that the limiting currents are 1amp and 20 amps respectively.

[0089] The positive electrode of the power supply was connected to theanode wires. The radio frequency bias electrode was cooled to 5° C. andconnected to an RF biasing power supply (e.g., PLASMALOC 3, from ENIPower Systems, Inc., Rochester, N.Y.). The entire vacuum chamber wasgrounded electrically. When pumping the chamber, the pressure in the oilreservoir was the same as the chamber pressure. The oil (adimethylsiloxane, 50 centistokes viscosit, 3780 molecular weight,available from Dow Corning under the trade designation “DC200”) wasde-aerated during chamber evacuation. After a de-aeration time of about15 minutes, air was introduced into the top portion of the oil reservoiruntil a pressure of 325 Pa was obtained. The 22 gauge oil deliveryneedle was maintained at 20° C. resulted in an oil feed rate of 0.36ml/minute. The oil evaporator was heated to about 370° C. One hundredfifty sccm of argon was introduced into the point source cathode and astable plasma was generated and sustained at minus 100 volts and 15amperes. The chamber pressure was between 0.13-0.26 Pa. At a web speedof about 3 meters/minute a series of experiments was conducted byvarying the bias power as shown in FIG. 6.

[0090] As shown in FIG. 6 the barrier properties of the plasmapolymerized silicone coatings improved with increasing bias voltage andwattage. Contact angles of all the coatings were measured around 95°(water). The contact angle of the uncoated PET film was 75°.

[0091] An additional sample of the same oil was prepared at a biaswattage of 400 Watts and a speed of 6 meters/minute. An eleven layercoating (Sample A) was obtained by reversing the web direction fivetimes. The coating thickness was about 3800 Å as measured by stepprofilometry of a simultaneously coated silicon chip placed on the PETfilm. Based on the eleven layer coating sample, the single layercoatings were estimated to be around 690 Å. The coating of Sample A wasanalyzed by Rutherford backscattering for elemental analysis. Theanalysis yielded in atom percent: C, 30%; Si, 30%; and 0, 40%. Thetheoretical yield for monomethylsilicone having a formula of—(Si(CH₃)_(½))O)_(n−)in atom percent is: C, 28.6%; Si, 28.6%; and 0,42.8%. This data, and the IR spectrum, the peak positions of which arelisted in Table 6, below, suggest that Sample A has a compositionsimilar to that of monomethylsilicone.

[0092] Table 2 below shows the Taber Abrasion Test results of theuncoated PET film and the one and eleven layer coatings on PET filmprepared at bias wattage of 400 Watts. The lower the percent haze, thegreater the abrasion resistance. Thus, abrasion resistance of the jetplasma silicone coatings increased with the increase in coatingthickness. TABLE 2 TABER (% HAZE) 1 LAYER 11 LAYERS CYCLES PET (690Angstroms) (3800 Angstroms)  0  0  0 0 20 8.5 5.5 2 40 12 8.5 4 60 1510.5  6.5 80 17 13 8 100  18 14 12 

[0093] The hardness of the eleven layer coating (3800 Angstroms) on asilicon wafer was 8.14 GPa. As shown below in Table 3, the hardness ofthe silicone coating was compared with that of an uncoated silicon chip,a glass microscope slide obtained VWR Scientific (catalog number48300-C25), and conventional monomethylsiloxane hard coat deposited asdescribed in Comparative Example A. TABLE 3 Coating ThicknessPenetration Depth Hardness Sample [Å] [Å] [GPa] 11 Layer Coating 38001730 8.14 Conventional by 5000-10,000 4927 1.33 Monomethyl- siloxaneHard Coat Glass Slide 2970 2.96 Silicon Wafer 1440 11.96

[0094] This data showed that the silicone coating was significantlyharder than the glass microscope slide, but softer than the siliconwafer.

[0095] The single layer silicone coatings prepared at 50 and 400 Wattbias power and the eleven layer silicone coating prepared at 400 Wattbias power were evaluated for their adhesion to the PET substrate film.Ninety degree peel strength measurements were conducted with aKRATON-based tape (Sealing Box tape #351 commercially available from 3MCompany, St. Paul, Minn.). The peel strength values were around 2.6kg/cm. Delamination occurred through cohesive failure of the adhesive.Therefore, the silicone coating/PET bonding exceeded the peel strengthvalues measured.

COMPARATIVE EXAMPLE A

[0096] The composition of conventionally prepared monomethylsiloxane wasfound to be similar to that of jet plasma polymerized silicone. However,when the properties of the conventional monomethylsiloxane coatings werecompared with those of certain jet plasma polymerized silicone coatings,significant differences were observed.

[0097] Monomethylsiloxane (Sample E) was prepared by the followingprocedure: 15 ml trimethoxymethylsilane ((CH₃O)₃CH₃Si) were added to 85ml water, the pH adjusted to 4 by glacial acetic acid and the mixturestirred for about 5 minutes until the solution became clear. One thirdof the solution was placed in an oven at 100° C. for 12 hours. Acolorless residue was obtained and used for several analyses: densityvalues were between 1.14-1.31 g/cm; the IR spectrum was nearly identicalto that of jet plasma polymerized silicone. WAXS identified a broad-peakat 8.7 Å. Hydrogen was determined by combustion analysis, which yielded4.2 wt-% H. Silicon was determined by gravametric and ICP analyses,which yielded 40.4 wt-% Si. Because the theoretical values formonomethylsilicone having the formula —-(Si(CH_(3½))O)_(n−)are 4.47 wt-%H and 41.9 wt-% Si, the sample appears to be monomethylsilicone.

[0098] The rest of the hydrolyzed trimethoxymethylsilane solution wasadjusted to a pH of 8-9 by adding several drops of 1 N KOH solution andused for the preparation of coatings.

[0099] Coating on silicon wafer: Silicon wafers were immersed in 3 N KOHsolution for about one minute, rinsed with distilled water and dipped inthe hydrolyzed trimethoxymethylsilane solution for 10 seconds. Thewafers were placed in an oven and heated for 12 hours at 100° C. Thecoating was not uniform in thickness and ranged according to theinterference colors from about 100 Å to several microns. The hardness ofthe coating was around 1.33 GPA.

[0100] Coating on PET film: The PET film (0.074 mm) was air coronatreated and dipped in the hydrolyzed trimethoxymethylsilane solution for10 seconds. The film samples were suspended in an oven and heated for 12hours at 100° C. A continuous coating was obtained. The thickness wasbetween 1-2 microns as measured by a film thickness gauge (SonyMagnescale Inc., Digital Indicator, U12A). The coatings did not have gasdiffusion barrier properties. Water vapor permeability values of thecoated and uncoated PET film were identical and around 8 g/(m²-day)(measured with a Permatran W-6 Permeability tester manufactured by ModemControls, Inc., Minneapolis, Minn.).

[0101] The following Table 4 summarizes the comparison in properties ofthe conventional monomethylsiloxane and the typical jet plasmapolymerized silicone. TABLE 4 Sample A Sample E Jet Plasma PolymerizedConventional Dimethyl Siloxane Monomethylsiloxane FTIR Spectrum showedthe same Spectrum showed the same peaks as for dimethyl peaks as fordimethyl siloxane precursor except siloxane precursor except change inabsorbance change in absorbance intensity for methyl and intensity formethyl and Si—O—Si peaks. Si—O—Si peaks. Experimental C = 30 atom % C =28.6 atom % Elemental Si = 30 atom % Si = 28.6 atom % Analysis O = 40atom % O = 42.8 atom % Theoretical H = 4.47 wt % H = 4.2 wt % ElementalSi = 41.9 wt % Si = 40.4 wt % Analysis Density 1.601-1.702 1.14-1.31[g/cm³] Hardness 8.14 1.33 [GPA] Water Vapor ˜0.01 8 Permeability [g/m²· day] WAXS Broad Peak at 7Å Broad Peak at 8.7Å

EXAMPLE 2

[0102] Carbon-rich coatings were deposited on 30 cm wide and 1.4×10⁻³ cmthick video grade polyethylene terephthalate (PET) film having thereinless than about 1% SiO₂ slip agent (OX-50 from Degussa of Germany),which had been corona treated and wrapped for storage and handling in apackaging film with moisture barrier characteristics (manufactured by 3MCompany, St. Paul, Minn.). The experiment was similar to Example 3 ofU.S. Pat. No. 5,464,667 (Kohler et al.), which is incorporated herein byreference, except that the hollow cathode slot was replaced by thehollow cathode point source (i.e., point source cathode) described abovein Example 1. The development of the point source cathode simplified thecathode system and eliminated several components of the hollow cathodeslot system, including the argon plasma compartment together with theargon plasma power supply and the acetylene compartment.

[0103] The point source cathode was placed about 17.5 cm away from thebiased chill roll. After the vacuum system was evacuated to about 1mTorr (0.13 Pa), 35 sccm argon and 1000 sccm acetylene were introducedtogether into the point source cathode. A stable plasma was generatedand sustained from the orifice of the cathode and expanded in cone shapetoward the deposition area. The DC pulsating power supply was set at 15amperes and minus 75 to minus 95 volts. The radio frequency biaselectrode was biased to minus 300 volts. The power consumption was320-400 watts. The web speed was about 15 meters/minute. The pressurevaried between 2.3 Pa and 3.0 Pa. The experiment was run for about 3-4hours during which no significant changes in the barrier properties ofthe coating was experienced. The water vapor permeability stayedconstant at around 1 g/(m²-day) as compared to an uncoated sample, whichhas a water vapor permeability of about 30 g/(m²-day). The extended timeperiod of a stable plasma (i.e., about 3-4 hours) is a significantadvantage of the point source cathode. Without the circular magnet thesmall orifice becomes plugged by carbon within several minutes.

EXAMPLE 3

[0104] Silicone coatings were deposited on 15 cm wide and 2.54×10⁻³ cmthick film available under the trade designation “KAPTON” film fromDuPont de Nemours (Wilmington, Del.), Type 100H. Except for the additionof an oil delivery system (described above) all other components of thedeposition system were identical to those described in Example I of U.S.Pat. No. 5,464,667 (Kohler et al.); however, the arrangement of thedeposition system was modified. The hollow cathode slot system was 9 cmaway from the chill roll. Drawing an imaginary horizontal plane from thecenter of the radio frequency bias electrode to the cathode, the cathodeslot was about 1.6 cm below the plane. The anode wire was about 4 cmaway from the cathode slot and about 6 cm below the imaginary plane. APyrex glass plate (20 cm wide, 5 cm long, 0.3 cm thick) was placedparallel to and about 0.6 cm below the imaginary plane reaching from thefront of the cathode box toward the radio frequency bias electrode andleaving about 4 cm between the glass plate and the front of the chillroll. The oil evaporator was positioned on the glass plate. Theevaporator slot was about 1.2 cm above the glass plate and about 4 cmaway from the chill roll. Another glass plate was placed upwards at a45° angle leaving a slot opening of about 1.5 cm between the glassplates. This arrangement allowed the oil vapor to be condensed andpolymerized on the film substrate that was in contact with the biasedchill roll. Subsequent condensation of oil vapor above the radiofrequency bias electrode was avoided to a high degree. The hollowcathode slot was about 15 cm wide and the graphite plates had a gap ofabout 0.6 cm. The radio frequency bias electrode was 5 cm in diameter,18 cm long, chilled to 5° C. The grounding box, i.e., anode, was about20 cm wide and included a 0.1 mm diameter tungsten wire. All powersupplies, including the anode. were connected to a common ground. Afterthe vacuum chamber was evacuated to a pressure of about 0.13 Pa, 100sccm argon was introduced into the argon plasma chamber, i.e., the firstcompartment of the hollow cathode slot system. The plasma was sustainedabout minus 450 volts and at a pulsating DC current of 0.5 amp using theAirco Temescal Model CL-2A power supply (maximum output of 0.5 amp). Thehollow cathode slot was powered by the 25 kilowatt nonpulsating filteredDC power supply from Hippotronics to enhance the argon plasma ignited inthe front compartment. The current was 8000 mA at about minus 100 volts.The Dow Corning DC200 silicone oil having a viscosity of 50 centistokes(cts) and a molecular weight of 3780 was vaporized according to theprocedure described in Example 1. About 50 cm Kapton film, as describedabove, was transported in loop form over the radio frequency biaselectrode and the two rolls of the web drive system. The deposition timewas determined from the web speed, the number of loop turns and thecontact area of the film with the chill roll. The length of the contactarea was 3.3 cm. The film accommodated silicon ships and germaniumcrystal to measure the special properties of the deposited silicone byelipsometry and FTIR spectroscopy, respectively. Variation in depositionparameters, in particular the bias power, resulted in significantdifferences in coating properties, as shows in Table 5. Table 5 showsthe difference in properties of a nonbiased Sample A and a biased SampleB. TABLE 5 SAMPLE SAMPLE A SAMPLE B BIAS WATTAGE 0 250 BIAS VOLTAGE 0−1400 DEPOSITION TIME 0.96 second 1.54 second DEPOSITION RATE 0.34cm/second 0.2 cm/second MOISTURE 55 g/m² · day 2.5 g/m² · dayPERMEABILITY ESCA Atom percent (O/C/Si) 29.6/48.4/22.0 29.9/48.8/21.2INDEX OF REFRACTION 1.327 1.464 THICKNESS 3595 Å 1252 Å

[0105] IR spectra of Sample B and DC200 silicone oil show the structuralchanges as a result of biased jet plasma polymerization. The positionand intensity of the absorption peaks are listed in Table 6 below. TABLE6 WAVE ABSORBANCE NUM- ABSORB- INTENSITY BER ASSIGN- ANCE RATIO SAMPLE(cm⁻¹) MENT INTENSITY (1260/1019) SILICONE 1019 Si—O stretch 0.397 0.980OIL 1091 Si—O stretch 0.326 1260 CH₃ rocking 0.389 mode B 1020 Si—Ostretch 0.670 0.578 1261 CH₃ rocking 0.387 mode 2151 Si—H stretch 0.011

[0106] Based on the absorbance intensity ratios, the biased jet plasmapolymerization reduced the methyl concentration of the coating by about40% and introduced some Si—H bonding. The lack of absorption peaks forC—H and C—H₂ moieties suggested band cleavage between the silicon atomsand the methyl groups and the subsequent polymerization of the formedsilicone radicals. As indicated by the ESCA results, oxygen appeared tobe involved in the polymerization, most likely resulting into Si—O—Sicrosslinkage. In comparison with the atomic percent ratio of aconventional silicone polymer that has a Si:C:O ratio of24.95:50.66:24.39, the oxygen concentration of sample B wassignificantly higher.

EXAMPLE 4

[0107] The deposition system, jet plasma conditions, and substrate werethe same as described in Example 3, except that the “KAPTON” film waswrapped around the chill roll. About 25% of the surface was exposed tothe plasma while the rest was covered with a nylon cover creating a gapof about 2 mm. The nylon cover was the same as that used in Example 1for the protection of the bare chill roll. DC200 silicone vapor was jetplasma polymerized onto the film for about 15 minutes while the radiofrequency bias electrode was rotating at about 10 rpm and was biased atabout 25 watts and minus 450 volts (sample A, which was preparedaccording to a process of the invention). In a second experiment thebias power was increased to about 250 watts and about minus 1200 volts(sample B, which was prepared according to a process of the invention).The coatings were scraped off the film and collected in powder form. Athird sample was collected from a glass plate positioned close to thechill roll. This sample was considered typical of a nonbiased jet plasmapolymerized silicone coating (Sample C, which was prepared according toa process of the invention). The data in Table 7 below compares thecarbon and hydrogen analyses of the different coatings. Table 7 alsoincludes the analysis of the DC200 silicone oil (Sample D, startingmaterial), the conventional monomethylsiloxane (Sample E, which wasprepared using a conventional process described in Comparative ExampleA), and density values of all the samples. TABLE 7 H:C Intensity of PeakSAM- WEIGHT WEIGHT atom Density (WAXS) PLE % C % H ratio (g/cm³) Before. . . After A 16.53 4.96 3.6 1.601-1.702 B 15.40 4.43 3.4 1.601-1.7027.2 C 30.31 7.84 3.1 <1.140 7.2 D 33.47 8.34 3.0 0.96 (from 7.2literature) E 1.14-1.31 8.7

[0108] Minor changes in the carbon and hydrogen concentrations occurredwhen the DC200 silicone oil (Sample D) was jet plasma polymerizedwithout bias (Sample C). A significant decrease in carbon and hydrogenconcentration was apparent for the biased samples (Samples A and B). TheC:H atom ratio was greater than three, which substantiated the FTIRspectroscopy results, namely the loss of methyl groups and the formationof Si—H bonding.

[0109] Samples A, B, C, D, and E were examined by wide angle x-rayscattering (WAXS) for purposes of identifying the presence ofcrystallinity. Data were collected using a Philips verticaldiffractometer, copper K_(α)radiation, and proportional detectorregistry of the scattered radiation. An interference peak on the orderof 7.2 Å was produced by all materials and is the only structuralfeature observed. The position of the interference maximum produced b,the oil did not change position upon polymerization. This indicates thatthe structural features present in the oil maintained their approximatearrangement after undergoing polymerization. The observed peak wassufficiently broad that the materials were not considered to possesscrystallinity, but rather possessed a structural feature that repeateditself on a 7 Å length scale. Amorphous carbon and amorphous silica,often used as barrier coatings, produce peaks at considerably higherangle, normally between 20 and 30 degrees (2Q), which correspond todistances on the order of 4.5-3 Å. These data indicated that thepolymerized material were distinctly different from amorphous carbon andsilica materials. A different structural feature was obtained fromSample E, which showed a broad peak at 8.7 Angstroms.

EXAMPLE 5

[0110] Nujol, an aliphatic hydrocarbon oil was deposited onto thesubstrate described in Example 3 using the system arrangement describedin Example 3. Except for the oil delivery, the procedure was also thesame. At a pressure of 1300 Pa in the oil reservoir the liquid wasintroduced into the evaporator heated at 280° C. The oil delivery needlegauge and temperature were 22° C. and 20° C., respectively. Four loopturns of the film were made within 123 seconds resulting in a depositiontime of 3.5 second. The pressure during jet plasma polymerization stayedmost of the time below 0.26 Pa. The water vapor permeability of thecoating, was around 40 g/(m²-day). This value was lower than the waterpermeability of the uncoated film (>55 g/(m²-day)) and thus indicatedbarrier properties of a hydrocarbon polymer. The IR spectra of thiscoating and the original Nujol showed minor structural chances. Thecorresponding absorbance intensity ratios varied between 10% and 20%.

EXAMPLES 6-8

[0111] The deposition procedure was similar to that described in Example3 except an acetylene/argon mixture was used as the jet plasma feed gasand a divider in the form of a glass plate was installed in between thetwo sources of acetylene/argon feed gas and silicone vapor. The seriesof examples illustrated the formation of multiple layer coatings andshowed changes in properties depending on the position of the divider.

EXAMPLE 6

[0112] The apparatus arrangement including the hollow cathode slotsystem, grounding box and radio frequency bias electrode were similar tothat described in Example 3. The oil delivery system consisted of asyringe pump, Teflon tubing (about 1 mm in diameter) connected to thesyringe and leading into the vacuum chamber, a 25 gauge microsyringeneedle connected to the Teflon tubing and inserted into the evaporatoras described in Example 1. DC 200 silicone oil (50 cts, Dow Coming Inc.)was fed at about 0.05-0.5 ml/minute into the evaporator heated at about350° C. It should be emphasized that due to imperfections in the earlystages of the development of the oil delivery system the exact amount ofoil available for evaporation and deposition could not be assessed fromthe flow rates indicated by the settings of the syringe pump. PET film(1.27×10⁻³ cm thick and 15 cm wide) was used as the substrate andcontinuously unwound from a first roll and rewound upon a second roll ata web speed of 3 m/minute. The divider was as close as possible to thechill roll, about 0.3 cm. The argon plasma was sustained at a flow rateof 50 sccm using a DC pulsating power supply at 0.5 amp and minus 475volts. The hollow cathode slot was powered by a 25 kW filtered DC powersupply from Hippotronics. At a flow rate of 200 sccm acetylene theplasma was sustained at about 8 amps and about minus 100 volts. Theradio frequency bias electrode was cooled to about 10° C. and biased atabout minus 1000 volts. A coating was obtained about 1350 Å thick. Thecoating on PET film has a static coefficient of friction of 0.15 andwater vapor permeability values of about 2.5 g/(m²-day). The FTIRspectrum of a coated germanium crystal (placed on the PET film) showedmainly absorption bands characteristic for silicone oil DC 200. Afterrinsing with toluene the silicone coating was completely removed, astrong evidence that no polymerization of the dimethyl silicone oil hadoccurred.

EXAMPLE 7

[0113] This example showed the importance and sensitivity of dividerposition for dimethyl silicone polymerization. Identical conditions wereused as those described in Example 6 except for widening the gap betweenthe divider and the film substrate to about 0.9 cm. The FTIR spectrumwas identical to that of Example 6. However, after thorough rinsing withtoluene about 75% of the coating was removed. This was an indicationthat the increased interaction of the plasma carbon with the dimethylsilicone vapor resulted in partly polymerized dimethyl silicone.

[0114] The partly polymerized silicone coatings were found to beexcellent lubricant coatings. Table 6 summarizes the static coefficientof friction values obtained on 1.27×10³ cm coated “KAPTON” film beforeand after soxhlet extraction (about 16 hours in toluene). The differentthicknesses were obtained by varying the web speed between about 1-18meters/minute. The thickness was estimated from the interference coloron coated silicone wafers. Table 8 shows static coefficient of frictionvalues that indicate a high degree of lubrication for extremely thincoatings and for a coating construction which contained both a highlypolymerized silicone portion (matrix) and a less polymerized orunpolymerized silicone oil. TABLE 8 Thickness (Å) 300 250 150 75 40 JPPolymerized Silicone Oil 0.06 0.06 0.10 0.09 0.10 JP PolymerizedSilicone Oil 0.04 0.06 0.11 0.13 0.14 after Soxhlet Extraction

EXAMPLE 8

[0115] This example confirmed the importance of sufficient dividerspacing for complete polymerization. Conditions were identical withthose in Example 7 except for the greater distance between the dividerand the substrate (about 1.5 cm). The FTIR spectrum was very similar tothe previous one. However, in contrast to Examples 6 and 7, rinsing withtoluene did not decrease appreciably the intensity of the FTIRabsorption peaks. Thus, the increased distance between the divider andthe substrate caused a sufficient interaction between jet plasma carbonand the dimethyl silicone vapor to warrant a fully polymerized,cross-linked dimethyl silicone structure with excellent adhesion to thesubstrate. The coating on PET film had a static coefficient of frictionof 0.23 and water vapor permeability values of about 1.5 g/(m²-day). Adepth profile of the coating on silicone wafers was conducted by AugerSpectroscopy. The spectrum showed two distinct layers: a carbon layeradjacent to the substrate and a silicone layer with a small interfacialregion between the carbon and the silicone layer as shown in FIG. 7.

[0116] The adhesion of the multi-layer coatings of Examples 6-8 wereevaluated by 90° peel strength testing and summarized in Table 9. In allcases delamination occurred at the interface between the coating and theadhesive tape. In particular, the high peel strength values obtainedwith samples of Example 8 indicated that the adhesion of the fullypolymerized dimethyl silicone layer to the carbon layer and also theadhesion of the carbon layer to the PET film substrate were at least 5.5N/dm or greater. The high adhesion and the intrinsic low surface energyvalues of the silicone coatings suggested their use for release coatingsand other low surface energy coatings. TABLE 9 Peel Strength (N/dm):Example 6 Unpolymerized DC 200 Oil 2.3 Example 7 Partly Polymerized DC200 Oil 2.7 Example 8 Fully Polymerized DC 200 Oil 5.8 PET FilmSubstrate (Control) 5.6

EXAMPLE 9

[0117] Polyperfluoroether (Fomblin) was another oil that was polymerizedwithout containing conventional, polymerizable functionalities.Multi-layer coatings were obtained with excellent lubricationproperties. Apparatus arrangement and process conditions were similar tothose in Example 7. Experimental evaporated Co/Ni thin film on a PETsubstrate (3M magnetic recording film) and 2.5×10⁻³ cm “KAPTON” filmwere used as substrates. The radio frequency bias electrode was biasedat minus 300 volts. The FTIR spectrum of the coating showed absorptionpeaks typical for Fomblin; however, when the coated germanium crystalwas washed in FC77, about 75% of the Fomblin was washed off. Thecoatings offered a unique multilayer construction in which the partialpolymerized polyperfluoroether top coat functioned as a lubricant andthe jet plasma carbon base as a protective and priming layer to thesubstrate. Table 10 shows the static coefficient of friction values independence of coating thicknesses before and after soxhlet extraction inFC77 (16 hours). In comparison, Sony Hi 8 ME Co/Ni tape had staticcoefficient of friction values between 0.26-0.32. TABLE 10 Thickness (Å)150 100 75 50 35 25 JP Polymerized 0.18 0.20 0.20 0.22 0.24 0.28Polyperfluoroether JP Polyermized 0.21 0.23 0.24 0.25 0.26 0.33Polyperfluoroether after Soxhlet Extraction

EXAMPLE 10

[0118] Homogeneous coatings were prepared by a procedure utilizing twofeed sources. This method provided the means to obtain new coatingproperties. Apparatus arrangement and process conditions were similar tothose described in Example 3. The hollow cathode slot and the evaporatorslot was placed parallel and in proximity of the radio frequency biaselectrode (less than 7 cm). A divider was omitted. A 2.5×10⁻³ cm thickand 15 cm wide “KAPTON” film obtained from DuPont type 100H was used asthe film substrate that was transported in loop form around the tworolls of the web drive and the radio frequency bias electrode formultiple deposition passes. The “KAPTON” film also accommodated siliconwafers. After the main vacuum chamber had been evacuated to a pressureof about 1 mTorr, 100 sccm argon was introduced into the argon plasmachamber, i.e., the first compartment of the hollow cathode slot system.The plasma was sustained at about minus 475 volts and a pulsating DCcurrent of about 500 mA. At a flow rate of 150 sccm, acetylene wasintroduced into the mixing chamber. i.e., the second compartment of thehollow cathode slot system. The hollow cathode slot was powered by asecond pulsating DC power supply. The plasma current was 1 amp at aboutminus 100 volts. The radio frequency bias electrode was cooled to about5-10° C. The bias voltage was minus 1500 volts. The dimethylsilicone oilwas introduced into the oil evaporator by way of a microsyringe pumpwith a feed of 0.05-0.5 ml/minute. A 25 gauge syringe needle was used.The run was completed after 20 passes. The coating was about 2800 Åthick and showed excellent water vapor barrier values of 0.17g/(m²-day). The contact angle and the static coefficient of frictionwere 99° and 0.22, respectively. The Auger depth profile showed auniform composition throughout the coating including carbon, silicon,and oxygen.

[0119] The present invention has been described with reference tovarious specific and preferred embodiments and techniques. It should beunderstood, however, that many variations and modifications may be madewhile remaining within the spirit and scope of the invention. Allpatents, patent applications, and publications are incorporated hereinby reference as if individually incorporated.

What is claimed is:
 1. A method for the formation of an organic coatingon a substrate comprising: providing a substrate in a vacuum; providingat least one vaporized organic material comprising at least onecomponent from at least one source, wherein the vaporized organicmaterial is capable of condensing in a vacuum of less than about 130 Pa;providing a plasma from at least one source other than the source of thevaporized organic material; directing the vaporized organic material andthe plasma toward the substrate; and causing the vaporized organicmaterial to condense and polymerize on the substrate in the presence ofthe plasma to form an organic coating.
 2. The method of claim 1 whereinthe step of causing the vaporized organic material to condense andpolymerize comprises: causing the plasma to interact with the vaporizedorganic material and form a reactive organic species; and contacting thesubstrate with the reactive organic species to form an organic coating.3. The method of claim 1 wherein the step of causing the vaporizedorganic material to condense and polymerize comprises: condensing thevaporized organic material on the substrate in the presence of theplasma to form reactive species that polymerize to form the organiccoating.
 4. The method of claim I wherein the substrate is in closeproximity to a radio frequency bias electrode such that the substrate isexposed to a radio frequency bias voltage.
 5. The method of claim 4wherein the radio frequency bias voltage is sufficient to provide thecoating with a density that is about 10% greater than the density of themajor component of the organic material prior to vaporization.
 6. Themethod of claim 4 wherein the radio frequency bias voltage is sufficientto provide the coating with a density that is about 50% greater than thedensity of the major component of the organic material prior tovaporization.
 7. The method of claim 1 wherein the vaporized organicmaterial comprises vaporized mineral oil.
 8. The method of claim 7wherein the plasma comprises a carbon-rich plasma and the vaporizedorganic material comprises vaporized dimethylsiloxane oil.
 9. The methodof claim 7 wherein the coating formed comprises a layer of a carbon-richmaterial, a layer of dimethylsiloxane that is at least partiallypolymerized, and an intermediate layer of a carbon/dimethylsiloxanecomposite.
 10. The method of claim 1 wherein the step of providing aplasma comprises generating a plasma in a vacuum chamber by: injecting aplasma gas into a hollow cathode system; providing a sufficient voltageto create and maintain a plasma within the hollow cathode system; andmaintaining a vacuum in the vacuum chamber sufficient for maintainingthe plasma.
 11. The method of claim 10 wherein the hollow cathode systemis a hollow cathode slot system comprising two electrode plates arrangedparallel to each other.
 12. The method of claim 11 wherein the hollowcathode slot system comprises a first compartment having therein ahollow cathode tube, a second compartment connected to the firstcompartment, and a third compartment connected to the second compartmenthaving therein the two parallel plates.
 13. The method of claim 12wherein the step of injecting a plasma gas comprises injecting a carriergas into the first compartment and a feed gas into the secondcompartment.
 14. The method of claim 13 wherein a plasma is formed fromthe carrier gas in the first compartment.
 15. The method of claim 13wherein a plasma is formed from the carrier gas and the feed gas in thethird compartment.
 16. The method of claim 15 wherein the feed gas isselected from the group consisting of saturated and unsaturatedhydrocarbons, nitrogen-containing hydrocarbons, oxygen-containinghydrocarbons, halogen-containing hydrocarbons, and silicon-containinghydrocarbons.
 17. The method of claim 10 wherein the hollow cathodesystem comprises a hollow cathode tube.
 18. The method of claim 10wherein the hollow cathode system comprises: a cylinder having an outletend; a magnet surrounding the outlet end of the cylinder; and a tubehaving a leading edge, wherein the tube is positioned inside thecylinder and recessed such that the leading edge of the tube is in theplane of the center line of the magnet.
 19. The method of claim 18wherein the magnet is made of a ceramic material.
 20. The method ofclaim 18 wherein the tube is made of a ceramic material.
 21. The methodof claim 1 wherein the plasma is formed from an inert gas.
 22. Themethod of claim 21 wherein the coating formed is a single layer oforganic material.
 23. The method of claim 21 wherein the polymerizedorganic material comprises a layer of multiple organic materials.
 24. Anorganic coating on a substrate preparable by: providing a substrate in avacuum; providing at least one vaporized organic material comprising atleast one component from at least one source, wherein the vaporizedorganic material is capable of condensing in a vacuum of less than about130 Pa; providing a plasma from a source other than the at least onesource of the vaporized organic material; directing the vaporizedorganic material and the plasma toward the substrate; causing the plasmato interact with the vaporized organic material and form a reactiveorganic species; and contacting the substrate with the reactive organicspecies to form an organic coating.
 25. The organic coating of claim 24which is one layer of a single organic material.
 26. The organic coatingof claim 24 which is one layer of multiple organic materials.
 27. Theorganic coating of claim 24 comprising multiple layers of differentorganic materials.
 28. The organic coating of claim 24 which is asilicone coating.
 29. The organic coating of claim 28 wherein thesilicone coating has a density of at least about 1.0.
 30. The organiccoating of claim 24 which is polymerized mineral oil.
 31. The organiccoating of claim 24 which has a density that is at least about 10%greater than the density of the major component of the organic materialprior to vaporization.
 32. The organic coating of claim 31 which has adensity that is at least about 50% greater than the density of the majorcomponent of the organic material prior to vaporization.
 33. Anon-diamond-like organic coating on a substrate comprising an organicmaterial comprising at least one major component, wherein the coatinghas a density that is at least about 50% greater than the density of themajor component of the organic material prior to coating.
 34. Thenon-diamond-like organic coating of claim 33 which has substantially thesame composition and structure as that of the starting material.
 35. Thenon-diamond-like organic coating of claim 33 which is one layer of asingle organic material.
 36. The non-diamond-like organic coating ofclaim 33 which is one layer of multiple organic materials.
 37. Thenon-diamond-like organic coating of claim 33 comprising multiple layersof different organic materials.
 38. The non-diamond-like organic coatingof claim 33 which is a silicone coating.
 39. The non-diamond-likeorganic coating of claim 38 wherein the silicone coating has a densityof at least about 1.0.
 40. The non-diamond-like organic coating of claim33 which is polymerized mineral oil.
 41. A jet plasma apparatus forforming a coating on a substrate comprising: a cathode system forgenerating a plasma; an anode system positioned relative to the cathodesystem such that the plasma is directed from the cathode system past theanode system and toward the substrate to be coated; and an oil deliverysystem for providing vaporized organic material positioned relative tothe cathode system such that the vaporized organic material and theplasma interact prior to, or upon contact with, the substrate.
 42. Thejet plasma apparatus of claim 41 wherein the hollow cathode system is ahollow cathode slot system comprising two electrode plates arrangedparallel to each other.
 43. The jet plasma apparatus of claim 42 whereinthe hollow cathode slot system comprises a first compartment havingtherein a hollow cathode tube, a second compartment connected to thefirst compartment, and a third compartment connected to the secondcompartment having therein the two parallel plates.
 44. The jet plasmaapparatus of claim 41 wherein the hollow cathode system comprises ahollow cathode tube.
 45. The jet plasma apparatus of claim 41 whereinthe hollow cathode system comprises a point source.
 46. The jet plasmaapparatus of claim 45 wherein the point source comprises: a cylinderhaving an outlet end; a magnet surrounding the outlet end of thecylinder; a tube having a leading edge, wherein the ceramic tube ispositioned inside the cylinder and recessed such that the leading edgeof the ceramic tube is in the plane of the center line of the magnet.47. The jet plasma apparatus of claim 41 further including a radiofrequency bias electrode in close proximity to the substrate to becoated.
 48. The jet plasma apparatus of claim 41 wherein the anodesystem is an adjustable anode system located substantially below thepath the plasma travels when in operation.
 49. The jet plasma apparatusof claim 41 wherein the oil delivery system comprises an atomizer forforming droplets of the organic material prior to vaporization.
 50. Ahollow cathode system comprising: a cylinder having an outlet end; amagnet surrounding the outlet end of the cylinder; and a tube having aleading edge, wherein the tube is positioned inside the cylinder andrecessed such that the leading edge of the tube is in the plane of thecenter line of the magnet.